Sustainable parts-per-million level catalysis with FeIII: One-pot cascade synthesis of 2,3-dihydroquinazolin-4(1H)-ones in water

A silica-supported iron complex has been identified as a highly active and reusable catalyst for the synthesis of medicinally important 2,3-dihydroquinazolin-4(1H)-ones. The catalyst was fully characterized by various spectroscopic analyses such as Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-VIS), scanning electron microscopy (SEM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), energy-dispersive spectroscopy (EDS) mapping, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), inductively coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis, Brunauer-Emmett-Teller (BET) isotherm and thermogravimetric analysis (TGA) analysis. A diverse library of 2,3-dihydroquinazolin-4(1H)-ones including some new analogues were successfully synthesized in good to excellent yields with parts-per-million (ppm) levels of Fe using water as a solvent. The active catalyst has high turnover number (TON) and turnover frequency (TOF) at the optimized condition, which were 30,087 and 30,087 h(-1), respectively. Ppm level catalysis, wide substrate scope, shorter reaction time, reusability of the catalyst, green solvent media and gram-scale synthesis make this protocol eco-friendly and sustainable.

Automated summary

A silica-supported iron complex has been identified as a highly active and reusable catalyst for the synthesis of medicinally important 2,3-dihydroquinazolin-4(1H)-ones. The catalyst showed high turnover number (TON) and turnover frequency (TOF), with successful synthesis of a diverse library of compounds in ppm levels of Fe using water as a solvent. The eco-friendly and sustainable protocol also demonstrated wide substrate scope, shorter reaction time, and gram-scale synthesis.